This study will compare giving a new drug called 3TC (Lamivudine) and ZDV (Zidovudine) together to giving DDR (Didanosine) alone or DDI and ZDV together. The use of 3TC and ZDV together has been tested in adults and children in other studies and has been tested in adults and children in other studies and has been found safe to use. The 3TC and ZDV otherther reduced how much HIV was in the patient's blood and increased the number of white blood cell that help the immunr system fight infection. the purpose is to see which one of the treatments does the best job of slowing down the HIV disease in children.